This invention relates generally to restraint systems for aircraft ejection seats, and more particularly to a restraint system which optimally and securely positions an aircrewman in an aircraft ejection seat prior to emergency escape from the cockpit.
High performance military aircraft are usually equipped with a catapult ejection seat which utilizes rocket thrust to propel it from the aircraft for emergency in-flight escape of aircrewman. A torso harness suit worn by the aircrewman over his flight coveralls serves both as a restraint system and a parachute harness. Typically, the harness suit includes a lap belt releasably connected to the lower seat portion, and shoulder straps attachable to an inertia reel mechanism fixed to the seat which permits free body movement during normal flight but automatically locks between 2 and 3 G's deceleration to prevent further forward movement. The inertial reel mechanism also includes a gas-actuated motor which forcibly draws the aircrewman's shoulders against the back of the seat prior to emergency ejection, the purpose being to insure that his spine is along the direction of acceleration of the seat.
Documented evidence has shown that injuries ranging from minor to severe still occur during or after egress due to improper restraint. See for example Report No. AMRL-TR-77-60, October 1977, entitled "F/FB-111 Escape Injury Mechanism Assessment" by Leon E. Kazarian, Aerospace Medical Research Laboratory, Aerospace Medical Division, Air Force Systems Command, Wright Patterson Air Force Base. Many of these injuries are attributable to an improperly fitted or loosely worn torso harness suit. A loosely worn harness suit causes the aircrewman to slide forward and under the lap belt and tilt his head forward. Under a high ejection force, this posture is highly susceptible to acute hyperflexion in the lumbar and cervical regions of the spine. Improper fit of the harness suit also diminishes effectiveness of the inertia reel retraction during positioning, induces flailing of the arms and legs in the windstream, and imposes additional shock loads on the aircrewman during parachute opening.